Análise da composição florística e da fitossociologia de uma área da caatinga.

Abstract

The caatinga is the predominant vegetation of the Brazilian semiarid region, a strong characteristic of this vegetation are its anatomical, morphological and functional characteristics of the flora that are able to adapt to adverse climatic and soil conditions of the region to survive, grow and develop. The objective of this study was to analyze the floristic composition and phytosociology of a caatinga fragment at “Fazenda Cana Brava”, municipality of Farias Brito, Ceará. The data were obtained from forest inventory with entirely random sampling, in which 11 sample units of 20 m x 20 m were allocated according to the Protocol of Measurements of Permanent Parcels of the Caatinga Management Network. All individuals in the plots with a chest height greater than or equal to 6 cm were sampled, measuring the circumference at baseline and at the level of the chest and the height of the individuals. From this, floristic composition, diversity, horizontal structure, vertical structure, phytosociological value and sociological position were evaluated. The most representative families were Fabaceae (66.45%), Euphorbiaceae (23.77%) and Combretaceae (5.20%), contributing to the richness of the studied area. The diversity index of Shannon (H') found in the study area was 1.80 nats.ind-1e and the Pielou (J) equability presented a value of 0.62. The species Mimosa caesalpinifolia Benth., Croton blanchetianus Baill. and Poincianella pyramidalis (Tul.) LP Queiroz were the most important for the studied area, with high density (76.45%) and dominance (71.98%), as well as higher importance value (62.40%), value phytosociological and sociological position. The diametric distribution of the area is in line with the behavior of natural populations, characterizing an inverted J, with a high concentration of individuals in the lower classes. The vertical stratification shows a good rate of representatives in the three strata, except the species Amburana cearensis (Allemão) A. C. Sm., Cassia rustina (Schrad.) Schrad. and Zenthoxylum stellerum Turcz., Ximenia americana L., which occurred only in one stratum of the three evaluated, which may characterize disturbances in the ecological succession of the area.